glibc/sysdeps/unix/sysv/linux/powerpc/powerpc64/be
Adhemerval Zanella Netto 6f4e0fcfa2 stdlib: Add arc4random, arc4random_buf, and arc4random_uniform (BZ #4417)
The implementation is based on scalar Chacha20 with per-thread cache.
It uses getrandom or /dev/urandom as fallback to get the initial entropy,
and reseeds the internal state on every 16MB of consumed buffer.

To improve performance and lower memory consumption the per-thread cache
is allocated lazily on first arc4random functions call, and if the
memory allocation fails getentropy or /dev/urandom is used as fallback.
The cache is also cleared on thread exit iff it was initialized (so if
arc4random is not called it is not touched).

Although it is lock-free, arc4random is still not async-signal-safe
(the per thread state is not updated atomically).

The ChaCha20 implementation is based on RFC8439 [1], omitting the final
XOR of the keystream with the plaintext because the plaintext is a
stream of zeros.  This strategy is similar to what OpenBSD arc4random
does.

The arc4random_uniform is based on previous work by Florian Weimer,
where the algorithm is based on Jérémie Lumbroso paper Optimal Discrete
Uniform Generation from Coin Flips, and Applications (2013) [2], who
credits Donald E. Knuth and Andrew C. Yao, The complexity of nonuniform
random number generation (1976), for solving the general case.

The main advantage of this method is the that the unit of randomness is not
the uniform random variable (uint32_t), but a random bit.  It optimizes the
internal buffer sampling by initially consuming a 32-bit random variable
and then sampling byte per byte.  Depending of the upper bound requested,
it might lead to better CPU utilization.

Checked on x86_64-linux-gnu, aarch64-linux, and powerpc64le-linux-gnu.

Co-authored-by: Florian Weimer <fweimer@redhat.com>
Reviewed-by: Yann Droneaud <ydroneaud@opteya.com>

[1] https://datatracker.ietf.org/doc/html/rfc8439
[2] https://arxiv.org/pdf/1304.1916.pdf
2022-07-22 11:58:27 -03:00
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ld.abilist Linux: Use ptrdiff_t for __rseq_offset 2022-02-02 22:37:20 +01:00
libanl.abilist resolv: Move libanl into libc (if libpthread is in libc) 2021-07-02 11:45:00 +02:00
libBrokenLocale.abilist
libc_malloc_debug.abilist Move malloc_{g,s}et_state to libc_malloc_debug 2021-07-22 18:38:10 +05:30
libc.abilist stdlib: Add arc4random, arc4random_buf, and arc4random_uniform (BZ #4417) 2022-07-22 11:58:27 -03:00
libcrypt.abilist
libdl.abilist dlfcn: Move dlopen into libc 2021-06-03 08:26:04 +02:00
libm.abilist math: Remove the error handling wrapper from hypot and hypotf 2021-12-13 10:08:46 -03:00
libnsl.abilist
libpthread.abilist nptl: Remove remaining code from libpthread 2021-05-21 22:35:01 +02:00
libresolv.abilist resolv: Move res_query functions into libc 2021-07-19 07:56:57 +02:00
librt.abilist Linux: Move timer_settime, __timer_settime64 from librt to libc 2021-06-28 09:51:01 +02:00
libthread_db.abilist
libutil.abilist login: Move libutil into libc 2021-06-30 08:43:37 +02:00